OK, I figured out what's up.
It isn't a Firefox or IE issue.
I am only having the logging-in problem when I am hitting MyFT via
http://64.78.185.85/forum/usercp.php?
I am not having the problem when I hit
http://www.flyertalk.com/forum/usercp.php
Now, I know you're gonna say, "Well why don't you just use the flyertalk.com domain?"
The only way I can access FT at work is through the IP b/c the FT url is blocked. Any suggestions w/ this info?